Bazaar is a distributed version control system. Bazaar runs on GNU/Linux, UNIX, Windows and OS X out of the box.
Bazaar is a distributed version control system that Just Works. While many similar systems require you to adapt to their model of working, Bazaar adapts to the workflows you want to use, and it takes only five minutes to try it out. People have used it to version pretty much anything: single-file projects, your /etc directory and even the thousands of files and revisions in the source code for Launchpad, MySQL and Mailman.
Bazaar runs on Windows, GNU/Linux, UNIX and Mac OS, and requires only Python 2.4. If you can run Python, you can run Bazaar! It is an official GNU project, licensed under the GPLv2 or later, at your option.